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Tropical Storm Flossie Discussion Number  27
NWS Central Pacific Hurricane Center Honolulu HI   EP072019
500 PM HST Sat Aug 03 2019
 
The satellite presentation of Flossie remains degraded this
afternoon. Pulsing deep convection is confined to the northeast
quadrant, and outflow remains restricted in the southwestern
semicircle. Subjective Dvorak current intensity estimates were
unchanged from the last advisory, ranging from 2.0 at SAB to 2.5 out
of JTWC and HFO, and CIMSS ADT was less than 2.5. These inputs all
suggest that Flossie is no stronger than 35 kt. However, an ASCAT
pass from this morning showed wind retrievals near 40 kt. Given the
unimpressive satellite presentation, the initial intensity will be
lowered to 40 kt. 

The low-level circulation center has been periodically obscured by
thin high clouds, but the center has been exposed enough to
obtain a fairly confident initial motion of 280/11 kt. During the
next 48 hours, Flossie is expected to be steered generally toward
the west-northwest by a low- to mid-level ridge to the north.
Thereafter, a turn toward the northwest and an eventual loss of
forward speed are expected, as the ridge weakens and Flossie
interacts with an upper-level trough parked north of Hawaii. The
forecast track was altered little from the prior advisory through 24
hours and was again nudged to the left at 48 hours and beyond,
bringing the weakening tropical cyclone closer to Hawaii. This
change keeps the forecast track closer to TVCN but still places it
toward the right side of the guidance envelope closer to the better
performing ECMWF. 

Flossie is expected to gradually weaken during the next few days.
Flossie remains under an upper-level ridge this afternoon, but it
has not been able to produce any sustained increase in deep
convection due to outflow aloft remaining largely confined to
north and northeast quadrants. Flossie will move north of the
upper-level ridge axis tonight and begin to encounter increasing
southwesterly vertical wind shear. The wind shear will increase to
around 30 kt by tomorrow and will remain in place throughout the
forecast period, leading to a steady weakening of Flossie. The
intensity forecast is mainly an update of the prior forecast,
weakening Flossie to a tropical depression Sunday night and to a
remnant low Tuesday. The forecast closely follows IVCN and weakens
Flossie at a slightly slower rate than SHIPS and LGEM.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  04/0300Z 18.9N 145.6W   40 KT  45 MPH
 12H  04/1200Z 19.3N 147.1W   40 KT  45 MPH
 24H  05/0000Z 19.6N 149.3W   35 KT  40 MPH
 36H  05/1200Z 20.0N 151.6W   30 KT  35 MPH
 48H  06/0000Z 20.6N 153.9W   30 KT  35 MPH
 72H  07/0000Z 22.9N 157.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  08/0000Z 24.3N 159.4W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  09/0000Z...DISSIPATED
 
$$
Forecaster Wroe
 
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